Yeah, best to think of it as a "two step" or "Two stage" technique. Using your same (one) foot, you go to sweep uke's first foot, either as an initial feint or it fails, then you sweep uke's second foot. i.e. extending your leg across, behind uke's first leg to sweep the back of his 2nd foot. You said "kosoto gari", correct?

Humm??? I'm not sure, would anyone consider it a "nidan kosoto gari" if you execute a "two step" sweep attempt with your one foot on uke's same foot? Hummm??? That would just be bad technique, now wouldn't it? cuz instead of taking two shots at uke's same foot you'd just "stick with it" until the sweep worked and uke went down. Correct? I mean you wouldn't "let up and off" with your foot making contact with uke's foot, and then try a second time. Would you?

So "nidan kosoto gari" must be to uke's other far foot.

Well I don't think this video shows "nidan kosoto gari" eventhough it is Titled that. But I'll let the Experts weigh in. This looks like Tani Otoshi to me. But what do I know. http://www.youtube.com/watch?v=xR0tdGxHq7w

A lot of people seem to take the term "nidan" to mean..... attacking the far leg only. But as your first replier stated it should be a "two step" process. So I'm still looking for an appropriate video. Unless your first replier was saying that you, tori, are taking "two steps", going through a "two step" process, when you attack uke's far leg. Cuz the following video, next line below, calls itself a "two step minor outer reaping". But hang on, I'll have to find clips on Mifune doing it.

Here's another video, again going to the far leg/foot, from behind only....http://www.youtube.com/watch?v=ThnRURNLWV0

In my opinion, and you can let the Experts on here weigh in, the other videos I presented to you above, the tori is taking liberty with using the term "nidan kosoto gari" when in effect they are either doing a Tani Otoshi or a Kosoto Gari to the far leg of uke. There being no "nidan", i.e. "two step" or "two stage" process involved, but rather a "single" direct attack to uke's far leg.

But again, I leave to the handful of "Pros" in here to comment, and give you the truth. But this is how I see it.